1. Field of the Invention
The present invention relates to a material for an inkjet ink composition applicable to inkjet technologies applied to printing materials, electroconductive materials, optical filter materials and biosensor materials, and to an inkjet ink composition using the material.
2. Discussion of the Background
An inkjet recording method forms a desired pattern image on a medium such as paper based on a computer signal. The recording method is widely used as the apparatus is simple and inexpensive because it can directly place ink on a recording medium and the ink is very efficiently used because of being directed only onto a place needing the ink. The inkjet recording method is used not only in general image forming (printing) fields but also in producing electronic devices such as thin film transistor and biosensor formations, e.g., formation of channels with an organic semiconductor material and formation of wiring patterns. In addition, the inkjet recording method is used for producing color filters such as liquid crystals in the field of electronic displays because material is efficiently used and can be precisely placed at a desired position. Further, it is applied in 3D modeling as well because of the same reasons.
However, in all these applications, shape variation of an ink drop after being dropped onto a substrate is an important control element, and it is preferable that the drop does not expand or bleed more than necessary.
The shape variations cause bleeding, color mixing, through-penetration in printing on paper; deterioration of image resolution and disfigurement due to more expansion than necessary and color mixing in printing on impenetrable paper (or resin); and operation failures due to defective channel formation and wiring short-circuits in electronic devices. Further, the shape variations cause ink fall and unnecessary expansion, resulting in deterioration of modeling resolution in 3D modeling.
In order to solve these problems, an associative compound is included in an ink. The associative compound typically forms a network with its multimolecular bonds to confine a liquid (in this case ink) within the network. Associative compounds have been used for a long time and properties thereof are disclosed in, e.g., “Industrial Chemical Magazine” 46th edition No. 8 published in August, 1943 P779 “Study on Sorbit derivative”; “Polymer Papers” Vol. 55 No. 10, P585 (1998) “Synthesis of low-molecular-weight gelator and its physical gel”; and “Polymer Processing” Vo. 45, No. 1, P21 (1996) “Oil Gelator”.
An ink including the associative compound forms a nonassociative (low-viscosity, sol, or liquid) shape at high temperatures, and an associative (high-viscosity or solid-like (gel or solid)) shape at low temperatures.
When an ink including the associative compound is discharged from an inkjet head, the ink is heated to have low viscosity. After discharge, the ink is cooled to increase its viscosity or gel, and which prevents the ink from penetrating and expanding.
Japanese published unexamined applications nos. 2005-126507, 2005-255821, 2005-325279 and 2005-330309 disclose ink compositions using the associative compounds. However, trials using the associative compounds in many different solvents (inks) have not been conducted. The present inventors have found that some ink compositions using the associative compounds do not have sufficient associative capability or do not have stable associativity at low temperatures (Examples 1 to 21 and Comparative Examples 1 to 18).
Japanese Patent No. 4233668 discloses an ink composition using trans-4-tertiarybutyl-1-phenylcyclohexanol as an associative compound. However, trials using the associative compound in many different solvents (inks) have not been conducted, and effects on optically active material are not disclosed. The present inventors have found that such ink composition does not have sufficient associative capability (Examples 98 to 107).
Japanese published unexamined application No. 2001-64556 discloses an associative compound in a meltable material and an associative compound having a siloxane structure. Japanese published unexamined application No. 2006-193745 discloses an application of an associative compound similar to the associative compound having a siloxane structure for use in the present invention to an ink composition. Further, Japanese published unexamined application No. 2008-266644 discloses using an associative compound having a specific structure including a siloxane structure in a meltable material. However, trials of associative capabilities of the associative compounds when actually applied to ink compositions have not been conducted, effects on optically active material are not disclosed, and trials using the associative compounds in many different solvents (inks) have not been conducted. The present inventors have found that siloxane compounds having two silicon atoms do not have sufficient stability at low temperatures (Example 118).
The associative materials for use in the present invention are disclosed in Japanese published unexamined applications Nos. 2004-182697, 2004-262856, 2004-262858 and 2002-080599 and Japanese Patent No. 4226979. Japanese published unexamined applications Nos. 2004-182697, 2004-262856 and 2004-262858 discloses forming an associative body in a silicone oil. Japanese Patent No. 4226979 discloses forming an associative body in a ferroelectric liquid crystal. Japanese published unexamined application No. 2002-080599 discloses an associative material applicable in various organic liquids. However, trials involving forming an associative body (solid-like body) in solvents for inkjet use have not been conducted, and particularly trials of associativity in a polymeric compound have not been conducted. Further, features of an associative organic group for a siloxane structure are not disclosed.
For these reasons, a need exists for a material for an inkjet ink composition that is capable of forming a stable associative structure in many different solvents.